Olefins are currently the largest volume chemical intermediates produced by the chemical industry, with a global annual production of over 300 billion pounds per year (Deng et al., Chem. Eng. Technol., 25:711 (2002)). Currently olefins are produced almost exclusively from fuels such as ethane or other light alkanes, such as naphtha, in a process known as steam cracking. This process takes place by homogeneous pyrolysis, typically at approximately 800 degrees Celsius (° C.). For ethane this process is represented by the reaction:C2H6→C2H4+H2 ΔHR=+136 kJ/mol.
It is estimated that about 30% of all pollution from chemical plants comes from steam cracking, due to CO2, NOx, and unburned hydrocarbons unavoidably produced during steam cracking. Furthermore, as many products can be formed as a result of pyrolysis, typical yields of ethylene from ethane are approximately 50%, with even lower yields typically observed for heavier alkanes.
As an alternative to steam cracking, it has been shown that partial oxidation of these fuels may be used to produce, for example, hydrogen and olefins, with the ability to provide a high selectivity to ethylene (Bodke et al., Science, 285:712 (1999); Beretta et al., J. Catal., 184:469 (1999)). Partial oxidation is an exothermic reaction that can be represented, for example, by the following reaction of ethane with oxygen:C2H6+½O2→C2H4+H2O ΔHR=−105 kJ/mol
As the reaction is exothermic, the expense of providing heat to the reaction may be reduced.
It has further been shown that higher alkanes, such as decane and hexadecane, for example, may be used as fuels to provide olefins with high selectivities using partial oxidation (Krummenacher et al., J. Catal., 215:332 (2003)).